Inkjet printers eject patterns of ink drops to form both single and multicolor printed images. In an inkjet printer, one or more printheads eject drops of ink onto an image receiving surface, such as paper or an indirect image receiving member, and the patterns of individual ink drops give the appearance of text, graphics, and other images. Some inkjet printers eject combinations of multiple ink colors, such as cyan, magenta, yellow, and black (CMYK) inks to form a wide range of perceptible colors in a printed image.
In some embodiments, a printer includes one or more printheads with arrays of inkjets that have a wider span along a cross-process axis than a corresponding width of a print medium that moves through the print zone during printing operation. Some print zones include an array of printheads that are arranged in a lateral “stitched” configuration to form a continuous array of inkjets that covers a region of the print zone that is wider than many types of print media used in the print zone. In other embodiments, a so-called full-width printhead is formed with a sufficiently large array of inkjets to span the width of an entire print zone with the single full-width printhead. For example, in one printer embodiment an array of printheads or a single full-width printhead extend approximately 44.5 cm across the print zone. In many instances, a print job uses a print medium that is narrower than the printhead array. For example, the print zone is noticeably wider than the dimensions of common paper sizes such as A4 sized paper (21 cm×29.7 cm) and Letter sized paper (21.6 cm×27.9 cm). During operation with existing printers, a media transport in the printer aligns the print medium with a portion of the inkjets in the printhead array and a digital controller uses only the inkjets that are aligned with the paper to form printed images while additional inkjets that are positioned beyond the edges of the printer remained deactivated when the dimensions of the print medium are smaller than the print zone.
While existing printers can accommodate a variety of different media sizes in the print zone, prolonged operation of the printer with narrower print media can cause some inkjets in the printhead array that do not eject onto the print media to become inoperable. Using the example print zone described above, an A4 sheet that passes through a 44.5 cm wide print zone with the longer edge (29.7 cm) arranged across the print zone leaves a 14.8 cm portion of the printhead array where inkjets in the printhead array are not aligned with the sheet and cannot eject ink drops onto the sheet. During a print job where the printer processes a large number of A4 sheets, the inkjets that are not aligned with the sheet remain deactivated for a prolonged period of time. During the prolonged period of deactivation, the liquefied ink in the inkjet pressure chambers and other fluid chambers and conduits within the printhead may solidify, develop air bubbles, or otherwise block the operation of the deactivated inkjets. During a subsequent print job that uses a larger media size, some or all of the previously deactivated inkjets may be inoperable and fail to eject ink drops onto portions of the larger print medium.
In existing printers, a printhead maintenance process can clear clogged or otherwise inoperable inkjets. The printhead maintenance process typically requires the printer to suspend regular printing operation and purge ink through the printheads to clear any blockages and prime the inkjets with liquefied ink for continued operation. Some printhead maintenance operations also use wipers or other printhead cleaning devices to clear clogged inkjets. Frequent printhead maintenance operations require consume both time and ink. In many printers that form printed images on different sizes of media during different print jobs, the frequent printhead maintenance operations reduce the effective printing rate of the printer and increase the consumption of ink that is not used for printing operations. Consequently, improved systems and methods for operating a printer to reduce the need to perform printhead maintenance operations while printing on different sizes of print media that are narrower than the width of one or more printhead arrays in the print zone would be beneficial.